Leaked versions of the BlackBerry OS 6 firmware have been available for months, but not everyone’s comfortable installing such software on their smartphone. For users who have been waiting it out for a legit upgrade, Sprint is now sending the update to users of the Bold 9650 and Curve 3G.

If you haven’t been following the advances RIM’s made to its operating system, version 6 adds a universal search, covering both locally stored data and the web, groups together subscribed RSS feeds and updates from social networking services, and updates its web browser with speed and compatibility improvements. Newer models like the BlackBerry Torch 9800 and Style 9670 come with OS 6 pre-installed.

Sprint’s updates for the Bold 9650 and Curve 9330 are now going out over-the-air, which means it may be a few days before your phone receives its update notification. For the impatient (and haven’t you really waited long enough already?) the upgrades are also available as downloads from RIM’s site. The Curve update is around 137MB, while the Bold’s weighs in at 157MB.

BB OS 6 updates for Verizon users are on their way, as well. A tipster spotted an official Verizon guide to upgrading the Bold and Curve at one of the company’s retail stores yesterday, making us think that the OTA update could go out any day now.

If you’ve managed to get OS 6 installed on your Bold or Curve, let us know what you think of the changes.